Multilayer electrical interconnection device and method of making same

ABSTRACT

A multilayer, monolithic electrical interconnection device includes a substrate and a plurality of overlaying, alternating conducting and insulating layers deposited atop the substrate and one another. The layers are deposited by thermal spraying of respective insulating or conducting material through defined apertures in respective spray masks. Interlayer electrical connections are intrinsically formed by direct metallurgical bonding between the conducting material of an overlaying layer and the conducting material of a previously sprayed layer.

TECHNICAL FIELD

This invention relates generally to multilayer electricalinterconnection devices. More particularly, the present inventionrelates to a multilayer electrical interconnection device and a methodof fabricating the same through the use of thermal spray technology. Thefabricated multilayer interconnection device is particularly suited foruse in the design and manufacture of high quality, low cost AutomotiveElectrical Distribution system components (AEDs) and AutomotiveElectronic Modules (AEMs) with high current carrying capability.

BACKGROUND

The use of circuit boards in manufacturing electronic equipment providesmany advantages, including minimal size and weight, high reliability,and suitability for automated production. A circuit board comprises aninsulating layer carrying conductive metal traces and bonding locationsfor electrical components. With advances in electronics, particularly inthe miniaturization of integrated circuits, a need for multilayer boardshas arisen to accommodate the high number of circuit interconnectionsper unit of surface area on a board.

Multilayer circuit boards utilize separate trace patterns on variouslayers in three dimensions and layer-to-layer interconnects (i.e., viasor plated throughholes) to implement complex interconnections in a smallspace. Multilayer circuit boards have been manufactured by laminatingseparate boards together and by a monolithic, plated-up technique. Thehigher cost and difficult production processes associated with prior artmultilayer circuit boards, however, have limited their utility.

The size and thickness of metal traces determines the magnitude ofelectrical current that can be safely carried. Thus, it would bedesirable to be able to arbitrarily control the size and thickness ofconductors within a multilayer structure to carry arbitrary amounts ofcurrent.

SUMMARY OF THE INVENTION

The present invention has the advantage of providing a multilayerelectrical interconnection device having a relatively inexpensive andsimple production method and resulting in a monolithic, multilayerdevice capable of carrying a relatively large amount of current.

In one aspect, the present invention provides a multilayer electricalinterconnection device and method of making the same by application ofthermal spray materials through positive and negative masks,respectively, to form conductive areas and vias, and insulating layerssuch that inter-layer direct metallurgical bonding between conductivelayers intrinsically result.

The device fabrication method includes the initial provision of asubstrate. Thereafter, a plurality of alternating insulating andconducting layers are deposited atop the substrate and one another bythermal spraying of respective insulating or conducting material throughccrrespondingly defined apertures in spray masks. Inter-layer electricalinterconnections are intrinsically formed by direct metallurgicalbonding between the conducting material of an overlying layer and theconducting material of a previously sprayed layer. The defined aperturesare formed through the use of positive and negative masking systems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a generalized schematic diagram illustrating the thermal spraymanufacturing technology used in accordance with the present invention.

FIG. 2 is a cross-sectional diagram of an electrical interconnectiondevice formed in accordance with the present invention.

FIG. 3 illustrates a positive mask arrangement for forming a conductinglayer in the structure of the present invention.

FIG. 4 illustrates a negative mask arrangement for forming an insulatinglayer in the structure of the present invention, wherein the layerprovides vias or interconnects between conducting layers.

FIG. 5 shows a positive mask in greater detail.

FIG. 6 shows a negative mask in greater detail.

FIG. 7 illustrates another embodiment for the construction of a negativemask.

FIG. 8 illustrates another embodiment for the construction of a positivemask.

FIG. 9 illustrates another embodiment for the construction of a negativemask.

FIG. 10 illustrates another embodiment for the construction of anegative mask.

FIG. 11 is a schematic diagram showing movement of a thermal spraynozzle to increase coverage of material during processing.

FIG. 12 is a schematic diagram of an automated manufacturing system usedfor the fabrication of multilayer electrical/electronic devices.

FIG. 13 is a perspective view of a finished interconnect device of thepresent invention.

FIG. 14 is a perspective view of an offset bond pad adapter.

FIG. 15 is a perspective view of a centered bond pad adapter.

FIG. 16 is a perspective view of a surface mount device of the type thatis soldered to the interconnect device of the present invention.

FIG. 17 is a perspective view of an interconnect device havingconnectors and bond pad adapters soldered thereto.

FIG. 18 is a perspective view of the device of FIG. 17 after populationof components onto the bond pad adapters.

FIG. 19 is a flowchart showing a preferred method according to thepresent invention.

FIG. 20 is a cross-sectional view of an interconnect device using aconductive substrate to provide ground connections.

FIG. 21 is a cross-sectional view showing a suspended mask aperture andthe resulting feature dimensions.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a thermal spray system for generating a thermal spray toselectably deposit insulating and conducting materials to manufacture aninterconnect device. A thermal spray comprised of carrier gases andparticles of selected materials is formed by heating particulates usingan electric arc or chemical combustion as a heat source. The thermalspray may be comprised of a plasma spray, high velocity oxy fuel (HVOF),two-wire arc (TWA), single-wire arc, or flame spray, for example.Layered structures are formed by alternately spraying insulating andconducting particles in predetermined patterns.

A thermal spray nozzle 10 receives material to be deposited from supplybins 11 and 12. The flow of material into nozzle 10 is selectablycontrolled using feeder valves 13 and 14, respectively. One bin maycontain particles of a conducting material (e.g., copper) while theother contains particles of an insulating material (e.g., alumina).Although a layered structure formed using material from just one bin foreach respective layer is described herein, it is also possible to formgraded structures wherein mixtures of materials are used for portions ofa structure.

Particles are heated, propelled by a carrier gas and directed out ofnozzle 10 as a thermal spray 15 for deposition. Thermal spray 15 isdirected toward a substrate 16 where the desired interconnect device isto be fabricated. Deposition is limited to certain desired areas byinterposing a spray mask 17 in the thermal spray particle stream priorto substrate 16. Mask 17 may preferably be laid on top of substrate 16(i.e., the bottom of mask 17 is flush with the top of the substrate ormost recently deposited layer) to provide sharp edges on the depositedfeatures. Mask 17 may be withdrawn away from substrate 16 as thermalspray material is deposited. There is typically no problem of the maskbecoming welded to the substrate since typical mask materials havesurfaces that are not well suited to joining with thermally sprayedmaterials. Specifically, mask materials have smooth surfaces to whichthermally sprayed material cannot adhere well (as described below, roughsurfaces are required to get thermally sprayed layers to stick).

Alternatively, mask 17 may be spaced away from substrate 16 in a fixedlocation at a distance at least equal to or greater than the thicknessof the layer then being deposited. This results in a device feature sizedifferent than the mask aperture dimension. Undercutting of the maskalong the aperture edges can also be used to prevent the mask fromattaching to the substrate. Modeling of feature size, including theeffects of mask to substrate distance and undercutting, is describedbelow with reference to FIG. 21.

By coordinated application of thermal spray 15 through respective spraymasks with various patterns to deposit alternating insulating andconducting layers, an interconnect device including conductive traces,conductive vias between layers, and insulating barriers separatingplanes of traces is formed.

The spray masks used in the invention can be roughly divided into twogeneral types: positive masks which are used to form conducting layersand which positively image the conductive traces in the structure, andnegative masks which are used to form insulating layers and which blockthermal spray substantially only in selected regions where conductivematerial is to remain exposed (e.g., vias, bonding pads, and testpoints). The resulting layers of thermal sprayed material are directlybonded together and form a monolithic, solid structure. Adjacent layersadhere to one another essentially by mechanical bonding, which isfacilitated by the rough surfaces resulting from thermal spraying.

FIG. 2 shows a cross-sectional view of the device of the presentinvention with multiple layers, including inter-layer electricalconnections which are formed by direct metallurgical bonding betweenconductive material sprayed during formation of different conductinglayers (i.e., at the sites of vias).

The intrinsic formation of metallurgically bonded inter-layer electricalconnections without reliance upon external devices provides significantcost and reliability advantages. Similarly, reliability problemsassociated with PWB plated-throughholes, flex circuit inter-layerconnections, and solder-based inter-layer connections are avoided.

The structure of FIG. 2 is built up by thermal spraying over a substrate20. A wrought or die cast aluminum plate provides a preferred substrate,and may comprise a wall of an enclosure for an electronic module. Aplanar insulating base layer 21 is deposited over substrate 20 toprevent subsequently deposited traces from being short circuited bysubstrate 20. If an insulating substrate is substituted, then insulatingbase layer 21 may not be necessary.

When aluminum is used as a substrate, the surface of the aluminum mustfirst be cleaned for thermal spray deposition of materials because thealuminum surfaces are naturally coated with a thin layer of smoothaluminum oxide. The smooth aluminum oxide can be cleaned from thesurface using a technique such as blasting with grit, etching, orspraying with a water jet. Only the underlying substrate needs suchcleaning or roughening since each subsequently sprayed layer hasintrinsic roughness that facilitates adherence of an overlying layer.

A first conducting layer 22 is deposited over base layer 21 in a patternwhich includes open spaces between separate circuit traces. A firstpatterned insulating layer 23 is deposited over layer 22 in a patternwhich leaves a selected region of conducting layer 22 uncovered so thatat least one of its traces can be subsequently connected to otherconducting layers or external components.

In the alternating structure of the device, a conducting layer 24 isdeposited over layer 23 in a respective pattern of circuit traces. Aninsulating layer 25 covers a portion of the previous layers. A finalconducting layer 26 is shown during deposition of conducting particles27 in a thermal spray being controlled by a pattern in a mask 28. Layer26 is deposited of the selected region to form a via between conductinglayers 22 and 24. The mask patterns are further selected to form bondingpads of conducting material to facilitate external connections as isdescribed below. A final insulating layer or other conformal coating maybe provided over exposed traces for protection (while leaving bondingpads exposed). In addition to conformal coating known in the art, it ispossible to thermally spray a thermosecting epoxy as a conformalcoating.

FIG. 3 shows the spatial relationship between nozzle 10, positive mask17, and substrate 16 whereby a conducting layer 30 having a desiredpattern is formed by virtue of a corresponding pattern 31 in mask 17.Likewise, FIG. 4 shows the spatial relationship between nozzle 10, anegative mask 32, and substrate 16 whereby a subsequent insulating layer33 having a desired pattern is formed by virtue of a correspondingpattern 34 in mask 32.

Process parameters, such as energy input to the thermal spray (i.e.,temperature), mask-to-substrate distance, particle size, and particlestream density, are controlled depending upon the desired finalstructure and materials selected. Particle stream density in particularcan be optimized for providing sharp edges to deposited features. Sinceturbulence, backscattering and other interactions can cause migration ofsome particles outside the desired pattern, a minimum distance betweenadjacent conducting traces is required to avoid electrical leakage andsurface breakdown depending upon the particular process parameters beingused.

A first embodiment of a positive mask 40 will be described withreference to FIG. 5. Apertures 41 are formed in a mask blank having aframe 42 and a central sheet 43. The mask blank may be comprised ofstainless steel or beryllium copper, for example, and apertures 41 maypreferably be formed by photochemical etching, but alternatively byelectro-discharge machining or mechanical machining. Photochemicaletching techniques are preferred because the strength of the remainingmask structure may be greater than when other machining techniques areused. A mask can thus withstand repeated production cycles withoutbending, deforming, warping, or otherwise deteriorating in a way thatmight otherwise prevent the consistent control of feature dimensions.

FIG. 6 shows a photochemically etched negative mask having a frame 46and etched central sheet 47. Blocking features 48 are supported bybridges 49. Bridges 49 are formed as small as is practical to avoidunintended breaks or significant thickness reductions in an insulatinglayer. Bridges 49 or other support structure which is not to appear inthe deposited layer would not be laid flush on the substrate duringdeposition since material is to be deposited under them. Therefore,bridges 49 either do not extend to the bottom surface of the mask or themask itself is not laid flush but is instead maintained at a heightabove the substrate during thermal spraying.

An alternative negative mask structure is shown in FIG. 7 using a screen50 to provide a rigid support without substantial blocking of thethermal spray. In constructing a mask, upper and lower blanks 51 and 52having apertures corresponding to the desired blocking areas of thenegative mask are sandwiched around screen 50. Pre-sized blocking piecesare joined within the apertures to the upper and lower sides of screen50 so that the blocking features are correctly located. Joining may beby silver soldering, welding, screwing together, or adhesive bonding,for example. Screen 50 with blocking features 53 is then fitted to aframe with lower frame 54 and upper frame 55 resulting in a finishednegative mask 56.

FIG. 8 illustrates a positive mask formed by the technique of FIG. 7 inwhich the screen takes the form of a honeycomb mesh. The honeycombstructure provides a high ratio of open area to support structure area,sometimes referred to as the packing factor or openness factor.

Using the technique of FIGS. 7 and 8, it can be seen that the thicknessof the mask material can be made much greater than the thickness of thescreen. This reduces the relative blocking efficiency of the screen,thus giving better defined features on the interconnect device. Therelative thinness of the screen also facilitates thermal sprayingthrough the mask at various spray angles for even coating beneath thescreen areas.

FIG. 9 shows a negative mask formed using a honeycomb mesh.

FIG. 10 shows another alternative method for the production of anegative mask 60 having a suspended shadow aperture 61. In thisapproach, a wire matrix 62 is utilized to form a positive-locatingself-aligning suspension of shadow apertures. For example, perpendicularwires 63 and 64 held in position by frame guides 65 lock shadow aperture61 in place by means of corresponding grooves in shadow aperture 61which receive the wires. The wire matrix is of a fine dimension relativeto shadow aperture dimensions so that the flow of particulates throughthe wire matrix reaches the substrate substantially unobstructed. Asignificant advantage of this approach is that it provides accuratecontrol of shadow aperture locations and relatively straightforward maskfabrication. In the case of a mask having a large number of shadowapertures, however, this technique may be less useful since themultiplicity of crossing wires could force impractical machiningoperations in connection with the frame guides.

In depositing features using negative masks, it is necessary to avoidcreating shadows of the negative mask support structures because thefailure to deposit insulating material could lead to unintended shortcircuits between conducting layers. By making negative mask supportshaving a width (i.e., the support's smallest dimension in the plane ofthe mask) as small as possible, unintended shadowing of insulatingmaterial is also minimized. However, durability and reusability of themask dictate that at least a minimum support width be used. To preventshadowing in any case, the methods of angle spraying or planartranslation are also preferably used.

In angle spraying, the thermal spray nozzle is swept through smallangles relative to a direction normal to the surface of the substrate.For example, the nozzle may follow a conical path 67 during thermalspraying as shown in FIG. 11. By precessing the nozzle through a smallangle, thermal sprayed material "crosses under" the supports of negativemask apertures. For example, with a negative mask having a shadowaperture 0.100 inches square and supports of width 0.010 inches, theprecession angle and the distance between the substrate and negativemask can be selected to provide an actual shadowed region of about 0.080inches on the substrate while coating all areas beneath the supportswith insulating material.

In planar translation, the negative mask and/or substrate are movedrelative to each other during thermal spraying by a fixed nozzle. Theamount of relative movement is preferably greater than the width of thesupport structure, and most preferably is twice the width. In the aboveexample with a support width of 0.010 inches, a relative translation of0.020 inches creates the same size desired shadow region of 0.080inches. Translation occurs across the width of each support structure.Thus, where perpendicular support structures are present, translationoccurs by a suitable amount in each direction.

Whereas support structures are a necessary part of negative masks, theyare also sometimes used in positive masks for added strength anddurability. Angle spraying and planar translation are also used for suchpositive mask support structures.

FIG. 12 shows an automated manufacturing system for the fabrication ofmultilayer, thermal sprayed electrical/electronic interconnect devices.Automated system 70 utilizes a serial array of thermal spray stations71-75, each station responsible for deposition of one insulating orconducting layer. Because the system is modular, mask programmable andmay employ numerous raw materials, several advantages relative toexisting electrical/electronic technologies are realized. For example, asingle automated system may be used to produce differentelectrical/electronic products by simply changing masks, and if desired,raw materials. The automated system is controlled by software, so thatprocess controls may be modified for each product by uploading therequired strategy.

New products may be rapidly developed because spray masks may be quicklydesigned and fabricated using CAE and CAM methods, which translatecomputer generated mask drawings directly into numerically controlledmachine instructions.

An automated system of thermal spray manufacture has flexibility tochange process parameters such as raw materials, plasma gas flow,thermal spray powder carrier gas flow, thermal spray material flow,thermal spray composition, substrate cooling rate, substratetemperature, and layer thickness, among others.

Manufacture of devices using the present invention creates less waste incomparison to prior art technologies such as PWB or thick filmtechnology. Other than in the low volume production of masks, nosolvents (other than water), acids, etches, inks, volatile organichydrocarbons, photoresists, bonding agents, or plating solutions arerequired.

Relative to existing semiconductor manufacturing technologies, such asLaser direct-write Chemical Vapor Deposition (LCVD) and existingboard-level electronic module manufacturing technologies, such as PWB orthick film, the above-described thermal spray method exhibits anextremely high material deposition rate on the order of 0.001 inches persecond, over surface areas up to 250 square inches. By comparison, atypical LCVD deposition rate is 0.0000254 inches per second, over asurface area of 0.0016 square inches, resulting in a thermal spraydeposition rate per unit area approximately 6 million times greater thanthe LCVD rate. Thermal spray provides a significant competitiveadvantage for high volume, low cost production of electronic modules andelectrical system components.

Still further, in comparison with existing technologies such as thickfilm and PWB, thermal spray provides significant cost and manufacturingcycle time advantages because relatively thick conductive or insulatinglayers necessary to meet power handling and current carryingrequirements of common AED system components and AEMs are more easilyproduced. The multiple conductive ink deposition and bake cycles, asused in prior art thick film manufacturing, and expensive processes usedto produce thick (greater than 2 ounces copper) conductive traces,employed in PWB manufacturing, are eliminated. Thermal spray may be usedto produce layer thicknesses ranging from less than 0.001 inches togreater than 1.0 inch. A preferred layer thickness is about 0.007 inchesis a typical automotive application. Heat build-up during sprayinglimits the amount of material that should be deposited in a single passto about 0.0005 to 0.001 inches.

Thermal spray variable cost is low compared to existing technologiessuch as thick film, PWB or bus bar. Thermal spray technology also offerssignificant packaging advantages in relation to such technologies as PWBand bus bar because it can be used to produce "formed-in-place"electrical interconnection systems. In other words, the thermal spraymaterials are applied directly to the base package material (e.g., analuminum module enclosure) which acts as the substrate and heat sink.This produces significant advantages in terms of cost and packagingdensity because separate mechanical adapters, spacers and mountinghardware, as well as the packaging volume they occupy, are eliminated.

A formed-in-place interconnect device 80 is shown in FIG. 13. A wall 81of an enclosure acts as a substrate for deposition of alternatinginsulating and conducting layers. Various conducting layers include vias82, traces 83, and bonding pads 84. Connector terminals 85 of a bulkheadconnector 86 are soldered to respective bonding pads 84. Bonding padscan also be used for connection to other external devices such asvarious adapter terminals for terminal connections or for directsoldered connection to surface mount devices (SMDs).

The thermal-sprayed bonding pads may be formed in rows, a rowcorresponding to each deposited conducting layer, such that the bondingpads form multiple tiers of different heights relative to theenclosure/substrate. This tiered approach facilitates the attachment ofcomplex, multi-terminal connectors to the multilayer electricalinterconnect structure. This approach further allows the first formedelectrical interconnect layers to travel beneath the subsequently formedbonding pads (without forming an electrical connection or short circuitbetween layers), thus facilitating a high packing density and minimizingenclosure size.

FIG. 14 shows an offset bonding pad adapter having a solder end 90 forsoldering to a bonding pad and a terminal end 91 for connecting to aterminal blade of an electrical component or to a wire. Terminal end 91is offset to the side of the respective bonding pad. FIG. 15 shows acentered bonding pad adapter wherein a terminal end 92 is oriented overthe center of the respective bonding pad. FIG. 16 shows a surface mountdevice having ends 93 and 94 for soldering to respective bonding padswithin an electrical circuit.

FIG. 17 shows an interconnection device having connector terminals andbonding pad adapters soldered in place prior to mounting of componentsin the device. FIG. 18 shows the device of FIG. 17 with relays and fusesmounted to the bonding pad adapters.

The generalized fabrication method of the invention is shown in FIG. 19.In step 95, a substrate is prepared for receiving a thermal spray. Forinstance, if an aluminum substrate is used then the surface must beroughened to remove the smooth layer of aluminum oxide that wouldprevent adherence of thermal sprayed material. Unless the substrate iscomprised of an insulating material, a thermal spray insulativeundercoating is deposited in step 96.

A first thermal spray conducting layer is deposited in step 97 through amask having a first pattern. In step 98, a first insulating layer isdeposited over the first conducting layer through a mask having a secondpattern such that selected regions ("shadow regions") are not covered bythe first insulating layer.

In step 99, thermal spray deposition is used to deposit additional,alternating conducting and insulating layers for form interconnectsbetween bonding pads. Devices with up to four conducting layers havebeen fabricated with excellent results. A greater number of conductinglayers can be used, but the number of layers becomes limited by tracegeometries and the amount of space available to form vias betweenlayers.

In step 100, electronic components such as connector terminals, bondingpad adapters, and surface mount devices are soldered to the bondingpads.

In keeping with the invention, numerous materials are suitable for thethermal spray operation besides the copper and alumina discussed above.Material may be chosen for forming a surface suitable for direct bondingof semiconductor packages or chips; utilizing such methods as directcopper bond, eutectic die attach or conductive epoxy adhesion, etc. Thedirect bonding capability results in very high thermal dissipationcapacity, which provides significant advantages in terms of reducedpackage size and cost.

FIG. 20 illustrates an alternative embodiment of a layered structure foran interconnect device in which a conducting substrate is utilized as aground plane through interconnection with other conducting layers. Anelectrically conductive substrate 101 has an insulating undercoatinglayer 102 deposited thereon. However, a void 103 in layer 102 leaves aportion of conductive substrate 101 exposed so that a conducting layer104 forms a contact with substrate 101. The void area is maintainedduring deposit of a subsequent insulating layer 105 so that a furtherconducting layer 106 can also make ground contact with substrate 101.

This alternative embodiment helps simplify the layout of a circuit byeliminating special return-to-ground traces (which may even result in astructure requiring one less conducting layer than would otherwise benecessary). Using the module base plate as a ground plane facilitatesgood EMI/EMC performance.

As discussed earlier, it may be desirable or necessary to suspend a maskwithout contacting the substrate during deposition of various features.In a preferred embodiment, an angled spray from a precessing nozzle isused. Since thermal sprayed material then follows a trajectory which isnot perpendicular to the mask and substrate, a deposited feature createdby material flow through a mask aperture is larger than that maskaperture (spray dispersion contributes to the enlarging affect but to amuch smaller degree). It is desirable to model feature size so that amanufacturing process and masks can be designed to provide sufficientspace between features.

As shown in FIG. 21, a mask 110 includes an aperture with a dimensiond_(A). The aperture may further include an undercut 111 having anundercut angle β. Thermal spray is delivered by a precessing nozzle at aspray angle α. A substrate 112 receives a deposited layer 113 having afeature dimension d_(F). The distance between substrate 112 and thenarrowest portion of the mask aperture is designated d_(MS). Therelationship between mask aperture size and feature size is given by:

    d.sub.F =d.sub.A +2d.sub.MS tan(α).

Undercut angle β would typically be greater than spray angle α to helpprevent formation of thermal spray deposits on the undercut sides of theaperture. If angle β is less than angle α, then distance d_(MS) wouldinstead be measured from the bottom edge of mask 110 or whatever otherportion of the aperture that most confines the thermal spray.

By way of example, a conductive copper trace 0.100 inches wide and0.0100 inches thick is thermally sprayed onto an isoplanar substratecomposed of aluminum coated evenly with an insulating layer of alumina(Al₂ O₃). A typical spray angle of 30°, thermal spray deposition rate of0.0005 inches per second, and mask to substrate distance of 0.050 inchesare employed. The above formula is used to determine a mask aperturesize that creates the desired feature dimension. Thus: ##EQU1## Theprecession angular velocity of the nozzle should be sufficient tocomplete two full cycles during the deposition process to ensure thereare no unintended voids under any support structures of the mask.

For subsequently sprayed layers, the thickness of previously sprayedlayers may vary across the device. Therefore, the mask to substratedistance d_(MS) may be different when using the previous formula forobtaining various mask dimensions at various areas within a single mask.

What is claimed is:
 1. A method of fabricating a monolithic multilayerelectrical interconnection device, comprising the steps of:depositing aninsulating undercoat layer over a substrate of conducting material, saidinsulating undercoat layer including a void; depositing a firstconducting layer including conductive traces over said substrate bythermal spraying a conductive material through a first mask having afirst pattern; depositing a first insulating layer over said firstconducting layer by thermal spraying an insulative material through asecond mask having a second pattern such that selected regions of saidfirst conducting layer are not covered by said first insulating layer;and depositing a second conducting layer over said first insulatinglayer and said first conducting layer by thermal spraying through athird mask having a third pattern such that said second conducting layerincludes at least one of said selected regions; wherein at least oneconducting layer connects with said substrate through said void; wherebysaid selected regions provide interconnects between conducting layersthrough direct metallurgical bonding.
 2. The method of claim 1 furthercomprising the steps of:depositing additional alternating insulating andconducting layers over said second conducting layer by thermal sprayingin respective patterns.
 3. The method of claim 1 wherein said electricalcomponents comprise connector terminals.
 4. The method of claim 1wherein said electrical components are comprised of surface mountdevices.
 5. The method of claim 1 further comprising the stepsof:forming bonding pads within said conducting layers; and solderingelectrical components to respective ones of said bonding pads.
 6. Themethod of claim 1 wherein said electrical components are comprised ofadapter terminals.